Monkey visual field measurement system and visual field measurement method

ABSTRACT

The present invention relates to a system and a method for determining a field of a vision of a monkey. Its object is to provide a system and a method which can cause a monkey to effect accurate visual field determination like a human subject. To achieve the object, according to the invention, there is provided a system for determining visual field of a monkey, comprising: a head fixing unit (A) for fixing a chair ( 1 ) to be seated by the monkey and the monkey&#39;s head; an eye target display unit (B) for displaying a gazing point ( 2 ) at which the monkey is caused to fix its eye and displaying also an eye target ( 3 ) at a predetermined position within the monkey&#39;s visual field with a predetermined brightness; a gazing monitor unit (C) for monitoring the direction of the monkey&#39;s gazing; and a response lever ( 4 ) by which the monkey shows that it has recognized the eye target; wherein the head fixing unit (A) includes an attachment member ( 5 ) fixable to the top of the monkey&#39;s head, a support member ( 6 ) connectable to the attachment member ( 5 ), and a base member ( 7 ) for fixing the support member ( 6 ). There is also provided a method for determining a visual field of a monkey using this system.

TECHNICAL FIELD

The present invention relates to a system and a method for determiningfield of vision of a monkey.

BACKGROUND ART

Glaucoma, a disease generally caused by rise in blood pressure in theeye, gives damage to the visual nerve system, leading to a symptom ofloss of vision. Various medical products have been developed and putinto use as therapeutical agents for this glaucoma. In research anddevelopment of medical products in general, not limited to those of thetherapeutical agents for glaucoma, an efficacy test of the agent usinganimals as subjects is essential before it is put for use in a clinicaltest. Since glaucoma is a disease leading to loss of vision as describedabove, it is preferred that such efficacy test be effected in the formof determination of visual field. However, it is extremely difficult toconduct determination of visual field with high accuracy with using ananimal subject. Therefore, in actuality, the efficacy test has beenconducted not in the form of determination of visual field, but in theform of determination of ophathalmotonometry (eye blood pressure).

On the other hand, as an instrument for determining visual field, aHumphrey field analyzer is usually employed. This field analyzer wasdeveloped for determining visual field of human. In its use, a subjectis seated in front of an eye target display screen and instructed to fixhis/her eye on a gazing point illuminated at a substantially centerposition in the eye target display screen. Under this condition, an eyetarget is illuminated at a predetermined position in the eye targetdisplay screen, and when the subject recognizes this illumination, thesubject shows it by e.g. pressing a response button. During thisdetermination, the subject assumes a posture with his/her chin placed ona fixing platform for fixing the subject's head.

As described above, in the research and development of a therapeuticagent for glaucoma, the determination of visual field has an importantroll. Hence, there has been a need to develop a technique which allowsan efficacy test to be conducted by way of visual field determinationusing an animal subject. It is known that there exists close correlationof central cavity visual function between the human and the monkey.Then, if the determination of visual field with using a monkey is madepossible, this will help deduce the efficacy of the agent in a humansubject with higher accuracy, thus being very useful for the researchand development of therapeutic agent for glaucoma.

However, the above-described Humphrey field analyzer was developed fordetermination of visual field of humans. So, although this instrumentcan be appropriately used when smooth communication is possible betweenthe operator and the subject, it is difficult to use this fordetermination of visual field of a money with which communication is noteasy.

Further, in the determination of visual field, it is determined to whichlevel of illumination the subject can recognize each position in his/herfield of vision. The greater the number of points determined and thegreater the number of levels of brightness determined at the respectivepoints, the higher the accuracy of the measurement result. However, inthe case of the Humphrey field analyzer, considering the time periodwhen a human subject can keep his/her concentration in thedetermination, the instrument is designed so that the determination iscompleted in a short period of time. Therefore, it is not possible todetermine a threshold value with varying the brightness in smallincrements or to conform the reproducibility of the determined values.In this respect, the instrument is not satisfactory in terms of theaccuracy of the visual field determination.

For this reason, there has been a need for developing a system and amethod which allow accurate determination of visual field of a monkey.In addition, since the Humphrey field analyzer is expensive, there hasalso been a need for a less costly determining system utilizing ageneral-purpose instrument.

An object of the present invention is to provide a system and a methodfor determining visual field of a monkey, which allow high accuracydetermination of visual field of a monkey just like that of a humansubject.

DISCLOSURE OF THE INVENTION

A system for determining visual field of a monkey, according to thepresent invention, comprises: a head fixing unit for fixing a chair tobe seated by the monkey and the monkey's head; an eye target displayunit for displaying a gazing point at which the monkey is caused to fixits eye and displaying also an eye target at a predetermined positionwithin the monkey's visual field with a predetermined brightness; agazing monitor unit for monitoring the direction of the monkey's gazing;a calculating unit for analyzing data; and a response lever by which themonkey shows that it has recognized the eye target; wherein the headfixing unit includes an attachment member fixable to the top of themonkey's head, a support member connectable to the attachment member,and a base member for fixing the support member.

With the above-described construction, the attachment memberconstituting the head fixing unit is attached to the top of the monkey'shead. This eliminates need to apply an external force such as afastening force, to fix the monkey's head in position. As a result, nostress is given to the monkey and the visual field determination canproceed with the monkey being under a relaxed state.

Further, when the monkey is fixed by the top of its head, it is possibleto expect the following effect.

Normally, when the monkey moves its head without moving its entire body,this head movement usually occurs in the form of swinging of the headabout the neck to the right and left. Therefore, by fixing the topportion of the head which portion is the most distant portion of thehead from the neck, it is possible to resist such head movement of themonkey with the minimum possible force. As a result, the fixing of themonkey's neck requires only a small force. This is believed to decreasethe stress given to the monkey.

In addition to the above, the invention's system for determining visualfield of a monkey comprises the support member connectable to theattachment member and the base member for fixing the support member.Then, if these members are provided separately from the attachmentmember, for fixing the attachment member to the top of the monkey'shead, this requires only surgical attachment of this small attachmentmember thereto prior to the determination. Therefore, until the fixationof the monkey's head to the base member is completed, it is possible toreduce the feeling of discomfort to the monkey. Accordingly, the visualfield determination can proceed with the monkey being much relaxed, sothe visual filed determination result with high reliability can beobtained.

With the invention's system for determining visual field of a monkey,the head fixing unit can be configured to be out of the monkey's visualfield. With this arrangement of keeping the head fixing unit out of themonkey's visual field, it becomes possible not to restrict the monkey'svisual field, thereby to avoid interference with the visual fielddetermination. Further, another effect can be expected, i.e. effectiveprevention of loss of calmness of the monkey when it views the headfixing unit.

With the invention's system for determining visual field of a monkey,the support member can be adapted to be speedily connectable with theattachment member and adapted also to be length-adjustable. With thepossibility of speedy connection between the support member and theattachment member, it is possible to reduce the set-up time for thevisual field determination. As a result, the visual field determinationcan be started with keeping minimum the stress which may be given to themonkey during the time of set-up until the time of the visual fileddetermination. Further, the length adjustability of the support membercan accommodate size difference if any in the monkey's head. As aresult, the head can be adjusted in position so that it may be set toprovide an appropriate eyeball position.

With the invention's system for determining visual field of a monkey,the gazing monitor unit includes an infrared LED array for irradiatinginfrared beam to the pupil of the monkey's eye, and a CCD camera and theshape of the monkey's pupil imaged by the CCD camera is approximated toan oval with the center of the oval representing the center of thepupil, and a comparison calculation is made between the gazing point andthe position coordinates of the pupil obtained in advance by causing themonkey to fix its eye on a desired position adjacent the gazing point,thereby to continuously determine the direction of the monkey's gazingin realtime. This construction provides the following advantage.

Namely, as a gazing monitor unit employed in the conventionalophthalmological instrument, there is known e.g. a unit adapted forprojecting infrared beam to the cornea of the subject's eye and thenelectrically detecting any displacement of the infrared beam reflectedby the surface of cornea. However, such instrument requires a device forprojecting the infrared beam and it is also necessary to arrange suchdevice in alignment with the gazing. Hence, the instrument tends to becomplicated.

In this regard, according to the system of the invention which simplyirradiates the infrared beam to the cornea and effects image processingof the movement of the cornea captured by the CCD camera, theabove-described drawbacks of the conventional system are overcome andthe gazing monitor device can be simple and convenient. Especially, inthe case of the construction of the present invention, there is no needto arrange the component such as the CCD camera or the like on thegazing, so that there will occur no interference with the visual fielddetermination. Moreover, by continuously determining the direction ofthe monkey's gazing in realtime, the visual field determination resultcan instantly reflect the gazing data.

With the invention's system for determining visual field of a monkey,the system can further employ a general-purpose personal computer indata analysis. With this possibility of analysis using a general-purposepersonal computer, it is possible to provide a less costly determiningsystem, as compared with the conventional Humphrey field analyzer.

On the other hand, the invention's method for fixing a head of a testsubject animal is characterized in that after an attachment member isfixedly attached to a top of the head of a monkey, a portion of asupport member is connected to this attachment member and then thesupport member is fixed to a base member.

With this method, as described hereinbefore regarding thefunction/effect of the visual field determining system, no externalforce such as a fastening force is applied when the monkey's head is tobe fixed. Therefore, no stress is given to the monkey and the visualfield determination can be effected while the monkey is relaxed.

Further, since the attachment member and the support member can beconnected speedily to each other, the set-up time prior to the visualfield determination can be shortened, so that the visual fielddetermination can then proceed smoothly, without giving stress to themonkey.

Also, as the top of the monkey's head is fixed, only small force isneeded for fixing the monkey's neck, so that the stress given to themonkey can be further reduced.

Further, with the above-described characterizing means, the memberattachable to the monkey's head, i.e. the attachment member which issmall as a whole, may be surgically attached to the top of the monkey'shead in advance. For this reason, it is possible to reduce thediscomfort to the monkey not only in the daily life of the monkey, butalso when the monkey's head is completely fixed to the base member.Accordingly, the visual field determination can be carried out with themonkey being under a more relaxed condition. Hence, visual fielddetermination result with higher reliability can be obtained.

On the other hand, according to the invention's method of determining afield of a vision of a monkey comprises the steps of: seating the monkeyat a chair with an attachment member being fixed to the top of themonkey's head; connecting a portion of a support member to theattachment member; fixing the support member to a base member; and thenilluminating a gazing point in an eye target display screen placed infront of the monkey in response to the monkey's pressing a responselever; illuminating an eye target at a predetermined position in themonkey's visual field with predetermined brightness while the monkey isgazing at the gazing point and pressing the response lever; andreleasing the pressing of the response lever when the eye target isilluminated.

In case the top of the monkey's head is fixed, the stress given to themonkey can be reduced, so it can be expected to obtain measurement datawith high reliability, as described hereinbefore.

Further, by fixing the head, it is possible to avoid gazing failure dueto a movement of the monkey's head. As a result, the monkey can easilygaze at the gazing point and the stress to the monkey can be reduced,whereby measurement data with good reproducibility can be obtained.

Also, with this method which releases the pressing of the response leverwhen the monkey shows that it has recognized the eye target, it ispossible to reduce the response time. That is, the response lever isconstructed as a spring-urged mechanism. Hence, a positive pressingforce needs to be applied against the spring urging force when theresponse lever is to be depressed. On the other hand, releasing theresponse lever requires only the monkey's releasing the pressing force,whereby the response lever is automatically returned by the springurging force. Accordingly, the initiation of the activation of theresponse lever can be very much quickened, so an accurate response canbe made.

As described above, using the determining system which can reduce thestress to the monkey and which is easy to operate and which provides anaccurate response, visual field determination result with even higherreliability can be obtained.

With the invention's method of determining a visual field of a monkey,in addition to the above, for confirming whether the monkey is gazing atthe gazing point or not, an infrared LED array is used for irradiatinginfrared beam to the pupil of the monkey's eye, and a CCD camera is usedfor monitoring the monkey's pupil, the shape of the monkey's pupil beingapproximated to an oval, with the center of the oval representing thecenter of the pupil, and a comparison calculation is made between thegazing point and the position coordinates of the pupil obtained inadvance by causing the monkey to gaze at a desired position adjacent thegazing point, thereby to continuously determine the direction of themonkey's gazing in realtime.

With this characterizing means, as described hereinbefore regarding thefunction/effect of the visual field determining system, the methodemploys a convenient gazing monitor device and this device can bedisposed at a position not interfering with the visual fielddetermination. Hence, while the method is economical, it is yet possibleto obtain visual field determination result which instantly the gazingdata having high reliability.

Further, by using the visual field determining system described above,it is also possible to provide an efficacy determining method fortherapeutic agent for glaucoma.

By using the present system, visual field determination of a monkey canbe effected with accuracy, and progression condition or the like of lossof visual field can be grasped in details. For this reason, in researchand develop of a new drug for use in treatment of glaucoma, it ispossible to obtain sufficient experiment data for confirming efficacy ofthe new drug, prior to its use in a clinical test.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view showing a construction of a system fordetermining a field of a vision of a monkey relating to the presentinvention,

FIG. 2 is an explanatory view showing a procedure for fixing a monkey'shead, and

FIG. 3 is an explanatory view showing result of visual fielddetermination of a monkey.

BEST MODE OF EMBODYING THE INVENTION

(Summary)

The visual field determining system and method relating to the presentinvention are designed for a monkey as the subject. As describedhereinbefore, if determination of a visual field of a monkey is madepossible, this will be very useful for research and development of atherapeutic agent for glaucoma.

The invention's system for determining a visual field of a monkeyincludes the following major components.

First, the system includes a head fixing unit A for fixing a chair 1 tobe seated by a monkey and the monkey's head. For obtaining visual fielddetermination result with high reliability, it is essential to fix themonkey's head.

Next, the system includes an eye target display unit B, a gazing monitorunit C and a calculating unit 12. The eye target display unit B displaysa gazing point 2 at which the monkey is caused to gaze and displays alsoan eye target 3 at a predetermined position within the visual field ofthe monkey with a predetermined brightness. The gazing monitor unit Cmonitors the direction of the gazing of the monkey. This is because forvisual field determination the gazing point 2 as a stationary pointneeds to be looked at constantly.

The system further includes a response lever 4 by which the monkey showsthat it has recognized the eye target 3. This response lever 4 isnormally operated by a hand.

Next, the visual field determining system and the visual fielddetermining method relating to the present invention will be describedwith reference to the accompanying drawings.

(Fixation of Head)

According to the invention's method, as shown in FIG. 1 and FIG. 2, thetop of the monkey's head is fixed.

In order to fix an attachment member 5 to the top of the monkey's headin advance, the monkey is subjected to a surgical operation, in whichfirst the monkey's skull is exposed by incision of the skin of the headtop and then into this exposed skull a screw made of a material such asstainless steel, silicone or the like not inviting inflammation isdriven and thereafter to this screw the attachment member 5 is fixedlyattached. In this embodiment, as this attachment member 5, there isemployed a resin cement for dental treatment in which e.g. a cylindricalstainless steel element is embedded. The bonding among the screw, theskull and the attachment member 5 utilizes polymerization of the resin.After the surgical operation, the operated portion is left until curingof the resin cement is completed. The fixation of the head requires onlyinserting the bar-like support member 6 into the cylindrical stainlesssteel portion and fixedly threading thereto.

When determination of the visual field is to be effected, the supportmember 6 is attached to the attachment member 5 and further the supportmember 6 is fixed to the base member 7. This base member 7 is formedintegrally with the seat 1 to be seated by a monkey. For attachment ofthe support member 6 with the base member 7, e.g. a main portion of thebar-like support member 6 is inserted into an insertion hole formed inthe base member 7. And, the support member 6 can be fixed by using ascrew 8 or a clamp of various types or the like. With this construction,the height of the chair 1 seated by a monkey is adjustable in accordancewith a seated height of the monkey, so that the monkey can assume arelaxed posture.

Further, with the support member 6 which is length adjustable, adifference in the size of the monkey's head can be adjusted. As aresult, the position of the head can be adjusted so as to obtain anappropriate eye ball position.

In this way, with the construction of fixing the top of the head byusing the attachment member 5 and so on, no fastening force is appliedto the monkey's head. Thus, the stress given to the monkey can bealleviated.

Further, in the case of this construction fixing the head top, it ispossible to adapt the head fixing unit A to be out of the monkey'svisual field.

Moreover, in the case of the construction fixing the head top, thefollowing effect can also be achieved. When the head is moved withoutbeing accompanied by a movement of the entire body, this usually takesthe form of swinging movement of the head about the neck to the rightand left. Therefore, if the top portion of the head which portion ismost distant from the neck is fixed, it is possible to resist, with aminimum force, the force of the monkey which tries to move its head. Asa result, only a small force is needed for fixing the monkey's neck, sothat the components such as the attachment member 5 may be formedcompact. Accordingly, it is possible to minimize the discomfort felt bythe monkey, such as the discomfort of a foreign object being attachedhereto and the stress given to the monkey can be further reduced.

Incidentally, in this embodiment, the attachment member 5 is comprisedof the resin cement for dental treatment. However, the invention is notlimited thereto. Alternatively, this member may be comprised, forexample, of other type of rein having biocompatibility.

Further, by fixing the head, it is possible to avoid gazing failure dueto a movement of the monkey's head. As a result, it becomes alsopossible for the monkey to easily gaze at the gazing point. Hence, withreduction of the stress to the monkey, measurement data with goodreproducibility can be obtained.

(Fixing and Monitoring of Monkey's Gazing)

In order to fix the monkey's gazing, like the case of visual fielddetermination of a human, a small white gazing point 2 is illuminated ata substantially center position in an eye target display screen 9. Theillumination of the gazing point 2 and illumination of an eye target 3to be described later are controlled by using a personal computer.

Regarding the illumination of the gazing point 2, for obtaining visualfield determination data, the gazing point 2 is illuminated at aposition substantially in front of an eye to be measured.

During the visual field determination, the gazing of the monkey ismonitored by using e.g. the infrared LED array 10, the CCD camera 11,the calculating unit 12 for analyzing e.g. data of gazing position, etc.

Specifically, while infrared beam is irradiated to the monkey's eye byusing the infrared LED array 10, the pupil of the monkey is monitored bythe CCD camera 11. And, the shape of the pupil is approximated to anoval based on the shading distribution of this monitor image, thereby toobtain the center of this oval as the center of the pupil.

These components, i.e. the CCD camera 11 and infrared LED array 10 areprepared in two sets, so as to monitor the right and left eyesrespectively. The two sets are provided for monitoring of the right andleft eyes independently of each other.

The determination of the gazing direction is carried out as follows. Inthe eye target display screen 9, total of nine gazing points 2 can beilluminated for the purpose of calibration. Then, the monkey is causedto gaze at each point in advance, thereby to obtain coordinates data ofthe nine gazing points 2 on the eye target display screen 9 and data ofeach pupil position obtained by the CCD camera 11 in correlation witheach other. In an actual determination, based on these data, theposition of the pupil in the monitor image is converted into coordinatepoints on the eye target display screen 9 so as to confirm the directionof the gazing.

(Procedure of Visual Field Determination)

In order to sustain the monkey's concentration and also to keep constantluminosity of the ambience for improvement of accuracy of the visualfield determination, the visual field determination is carried outinside a sound-proof chamber 13. Various control instruments used in thevisual field determination are disposed in a control room 14 separatedfrom the sound-proof chamber 13. The condition and appearance of themonkey are monitored by a behavior monitoring camera 15 and a behaviormonitoring screen 16.

The interval between the start of the monkey's gazing at the gazingpoint 2 and the illumination of the eye target 3 is variedappropriately, so as to prevent the monkey from memorizing theilluminating timing of the eye target 3 and also to effectively sustainthe monkey's concentration.

The eye target 3 is illuminated in a random manner at each position inthe visual field and with appropriate variation of its brightness. Withthis, it is possible to know the limit of visual recognition at eacharea in the visual field.

The response lever 4 employed in the present embodiment is spring-urgedso that the lever may be returned upon release of the lever by themonkey. The monkey has been trained so that it shows its visualrecognition of the illumination of the eye target 3 by means ofreleasing the response lever 4.

With this method of releasing the pressing of the response lever 4, itis possible to reduce the response time. That is, the response lever 4is the spring-biased mechanism. And, for depressing this response lever4, a positive pressing force needs to be applied thereto against theurging force of the spring. On the other hand, when releasing theresponse lever 4, the response lever 4 can be immediately returned bythe spring urging force simply by the monkey's releasing its pressingforce. Therefore, the timing of initiation of the activation of theresponse lever 4 can be very quick, so an accurate response can beobtained.

The reliability of a monkey's response can be judged by checking thefollowing respects.

(1) whether the monkey's gazing was directed at the gazing point 2 ornot;

(2) whether the response time for the presentation of the eye target 3is appropriate or not; and

(3) whether an eye target 3 to which the monkey failed to respond was aneye target 3 that should have been recognized by the monkey or not.

Based on these judgment items, the eye target display control unit Beffects the judgment for each presentation of the eye target 3. When theresponse is judged as reliable, a reward such as juice will be given tothe monkey and at the same time a buzzer is sounded. The reward and thesounding of the buzzer are positive feedback for the monkey's response,which is believed to improve the monkey's motivation for the visualfield determination.

(Example)

For fixing a monkey's head, resin cement for dental treatment in which acylindrical stainless steel member was embedded was employed. As thisresin cement, a resin cement which can resist deterioration after lapseof long time period will be appropriate in order to prevent easyinadvertent detachment of the attachment member from the monkey's head.

For the visual field determination, first, the monkey is caused to gazeat the gazing point 2 illuminated in front of the monkey. While thisgazing point 2 is being gazed at, the eye target 3 is illuminated at apredetermined position within the visual field. During thedetermination, movements of the monkey's eyeball are constantlymonitored by the method described above.

The eye target 3 can be varied in its brightness by increment/decrementof 1 dB. The unit “dB” used here is a unit which is commonly employed bymany field analyzers as the unit of brightness. The unit “dB” representsrelative brightness and the maximum brightness of the field analyzer is0 dB. The brightness setting in this embodiment was done in accordancewith the Humphrey field analyzer. 0 dB corresponds substantially to thebrightness of sunshine. As the relative brightness is varied from thisto 1 dB 2 dB . . . , the brightness is reduced each time by 0.8 timeapproximately.

If the monkey provides reliable response such as response by releasingthe response lever 4 disposed near its hand within a predeterminedperiod following the illumination of the eye target 3 with a certainbrightness, a reward is given to the monkey.

FIG. 3 shows the result of determination carried out by the mannersdescribed above.

This data comprise visual field data of a right eye of a crab-eatingmonkey (11 years old male). The eye target presenting positions in thisdata were in accordance with the Humphrey Central 24-2 in clinical use.

The brightness of the eye target 3 at each determination point wasvaried stepwise by 1 dB. In doing this, there was employed a method(adaptive strategy) for varying the strength of presenting stimulationin accordance with a response from the monkey. The above-describedvisual filed data were arranged in order based on the determinationresult by using an average value of brightness of the eye target 3 ateach determination point at the timing of arrival at a threshold valuewhich is believed to indicate visual recognition, that is, equilibrium.

(Effect)

It has been shown that the use of the invention's system and method fordetermining a field of vision of a monkey permits accurate visual fielddetermination of the monkey.

And, by effecting a visual field determination of a monkey by using thepresent system, in e.g. development of a new drug for use in treatmentof glaucoma, it becomes possible to obtain experiment data forconfirming e.g. efficacy of the new drug prior to its clinical testusing a human.

Further, as the system can use a general-purpose instrument, the systemcan be inexpensive.

INDUSTRIAL APPLICABILITY

As described above, the invention's system and method for determining afield of a vision of a monkey are suitable for causing a monkey toeffect an accurate visual field determination. And, causing a monkey toeffect such accurate visual field determination is very useful forresearch and development of a therapeutic agent for glaucoma.

1. A system for determining visual field of a monkey, comprising: a headfixing unit (A) for fixing a chair (1) to be seated by the monkey andthe monkey's head; an eye target display unit (B) for displaying agazing point (2) at which the monkey is caused to fix its eye anddisplaying also an eye target (3) at a predetermined position within themonkey's visual field with a predetermined brightness; a gazing monitorunit (C) for monitoring the direction of the monkey's gazing; acalculating unit (12) for analyzing data; and a response lever (4) bywhich the monkey shows that it has recognized the eye target; whereinthe head fixing unit (A) includes an attachment member (5) fixable tothe top of the monkey's head, a support member (6) connectable to theattachment member, and a base member (7) for fixing the support member.2. The visual field determining system for a monkey according to claim1, wherein the head fixing unit (A) is configured to be out of themonkey's visual field.
 3. The visual field determining system for amonkey according to claim 1, wherein the support member (6) is adaptedto be speedily connectable with the attachment member (5) and adaptedalso to be length-adjustable.
 4. A system for determining visual fieldof a monkey, comprising: a head fixing unit (A) for fixing a chair (1)to be seated by the monkey and the monkey's head; an eye target displayunit (B) for displaying a gazing point (2) at which the monkey is causedto fix its eye and displaying also an eye target (3) at a predeterminedposition within the monkey's visual field with a predeterminedbrightness; a gazing monitor unit (C) for monitoring the direction ofthe monkey's gazing; a calculating unit (12) for analyzing data; and aresponse lever (4) by which the monkey shows that it has recognized theeye target; wherein the head fixing unit (A) includes an attachmentmember (5) fixable to the top of the monkey's head, a support member (6)connectable to the attachment member, and a base member (7) for fixingthe support member; the gazing monitor unit (C) includes an infrared LEDarray (10) for irradiating infrared beam to the pupil of the monkey'seye, and a CCD camera (11); the shape of the monkey's pupil imaged bythe CCD camera is approximated to an oval with the center of the ovalrepresenting the center of the pupil, and a comparison calculation ismade between the gazing point and the position coordinates of the pupilobtained in advance by causing the monkey to fix its eye on a desiredposition adjacent to the gazing point, thereby to continuously determinethe direction of the monkey's gazing in real-time.
 5. The visual fielddetermining system for a monkey according to claim 1, wherein saidcalculating unit (12) comprises a general-purpose personal computer. 6.A method of determining a field of a vision of a monkey comprising thesteps of: seating the monkey in a chair (1) with an attachment member(5) being fixed to the top of the monkey's head; connecting a portion ofa support member (6) to the attachment member; fixing the support memberto a base member (7); and then illuminating a gazing point (2) in an eyetarget display screen placed in front of the monkey in response to themonkey's pressing a response lever (4); illuminating an eye target (3)at a predetermined position in the monkey's visual field withpredetermined brightness while the monkey is gazing at the gazing pointand pressing the response lever; and releasing the pressing of theresponse lever when the eye target is illuminated.
 7. The method ofdetermining a field of a vision of a monkey according to claim 6,wherein for confirming whether the monkey is gazing at the gazing point(2) or not, an infrared LED array (10) is used for irradiating infraredbeam to the pupil of the monkey's eye, and a CCD camera (11) is used formonitoring the monkey's pupil, the shape of the monkey's pupil beingapproximated to an oval, with the center of the oval representing thecenter of the pupil, and a comparison calculation is made between thegazing point and the position coordinates of the pupil obtained inadvance by causing the monkey to gaze at a desired position adjacent tothe gazing point, thereby to continuously determine the direction of themonkey's gazing in real-time.
 8. A method of determining efficacy of atherapeutic agent for glaucoma using the visual field determining systemas defined in claim
 1. 9. A method for fixing a head of a test subjectanimal, wherein after an attachment member (5) is surgically attachedand fixed to the top of the head of the test subject animal to fix thehead of the test subject animal and determine the direction of thegazing of the test subject animal, a support member (6) is connected atone end thereof to this attachment member and is fixed at the other endthereof to a base member (7).